Among vehicle body substructures of vehicles such as automobiles has conventionally been that in which an undercover for covering the underside of a floor is mounted in a lower part of the vehicle. By mounting the undercover, the undersurface of the vehicle body is flattened to enhance the aerodynamic characteristics of the vehicle during its travel and improve the high speed stability and fuel economy of the vehicle.
In recent years, moreover, a proposal has been made for a structure in which a travel wind flowing rearward below the undersurface of the vehicle body is straightened by the shape of the undercover to improve the aerodynamic characteristics of the vehicle body. A concrete example is a structure in which a straightening protruding portion protruding downward from the surface of the undercover is provided ahead of a rear wheel suspension (see Patent Document 1).
Configurations as described above exhibit the action and effect of decreasing collisions between a suspension element and the travel wind flowing below the undersurface of the vehicle body, thereby reducing turbulence, by the rear wheel suspension, in the travel wind flowing in the center of a space in the width direction of the vehicle below the undersurface of the vehicle body.